P04EF
EVAP System Very Small Leak Detected Fresh Air Side
Same as P04EE on the fresh-air side - microcrack in a hose or imperfect vent valve seal at the most sensitive test threshold.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: easy
Symptoms
- Check engine light on
- Possible smell of fuel near tank or engine bay
- Failed emissions inspection
- Loose-cap warning may appear
Common causes
Ordered by how often each turns out to be the cause.
- Vent valve seal agedCommon
Parts involved
- EVAP Vent Valve
- EVAP Hose Fresh Air Side
P04EF is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.